It is standard to vent the output of the cooling fan on a power tool so that it blows chips and dusts away from the work area, giving a clear view of the place where the bit or blade engages the workpiece. When, however, the tool is of the light-duty battery-powered type no such cooling fan is provided, in particular when the bit or blade is reciprocated such construction does not lend itself to the simple addition of a fan blade.
German Pat. No. 1,094,968 describes a reciprocating-blade tool wherein a small piston-and-cylinder unit is provided that is coupled to the blade chuck. On each reciprocation of the chuck the piston is similarly reciprocated and the output of the unit is directed at the work area. Thus on each reciprocation of the tool, a gust of air is emitted that blows away dust and chips.
This latter arrangement is fairly complicated so that it adds considerably both to the cost and weight of the tool. Thus installation of such a unit in a battery-powered tool is not advantageous.